Should just go off, but might flicker on/off for a while if a progressive rather than sudden fault

What Mr.S said.

You occasionally get high loss causing an intermittent service ... think of it like an HR.

Do you now have your Gigaclear router installed and if so, what speeds to you get from this sites speed tests? What minimum broadband speed did Gigaclear promise when you ordered the service, and what was the estimated speed during busy periods?

(I have been happy with the Gigaclear service I have had for the past 5 years. BT Openreach have been telling me that they will also provide an FTTP service for the past 6 months but there has been no sign of any work locally. If they did provide a service it would likely be slower and more expensive.)

I 've got a Gigaclear installation since around 2015
As I dimly recall from discussions at that time......

Your Fibre loss of -8 sounds normal: mine I noted was -6
I vaguely recall they told me that once it gets as bad as -25 it no longer works

Thanks for that, it's reassuring to hear.

Very frustrating that after waiting years for an install, it happens when I'm stuck overseas and not around to check into it any further.